Updated Type check for shived innerHTML

[Nevraeka]

The "content" parameter for "innerHTML" was not coerced to a string in the event it is a "Number" type. IE8 internal handles this for standard elements.

[aFarkas]

Thanks. I just looked into it and I think the following line change would be shorter and more performant:

if (!elem.canHaveChildren || elem.document == ownerDocument || !html5.shivMethods || typeof content != 'string') {
    return innerDesc.set.apply(elem, arguments);
}

Note, I have only added the typeof content check.

[Nevraeka]

Cool. Sorry for the delay in checking this. Thanks